Compressed air usually contains a lot of water and saturated vapor, which are mainly removed by refrigeration dryer in tradition. In prior art drying means of the refrigeration dryer is: compressed air enters a drying pipe of the refrigeration dryer, and the drying pipe contacts a cooling pipe, so that heat exchange occurs between the compressed air in the drying pipe and the cooling pipe, thereby the saturated vapor in the compressed air condenses into water, which is removed by passing through a filtering device. However, such drying means is inefficient, has poor drying effect and high energy consumption, and additionally needs a filtering device to filter condensed water.